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I am building a new home (starting in 60 days) and just received a bid from a local Trane contractor. He included 3 options for this split system. One of the options was for a TXV. Through previous information on this site I have decided to include this option (local utility rebate also requires a TXV on this system). The other option is for an April Aire filter system. I'm still trying to decide about this one.

The last option was for a for something called "Tight Ducts". Not trying to be a smart alec but I assumed all ducts would be tight (not leak, that is). I'm going to call the contractor tomorrow and ask him what "tight ducts" means but I thought I would try to educate myself on the important issues relating to ductwork. Reading many posts on this site has convined me that proper duct work design and installation is one of the most important and often over looked aspects of a good HVAC job. I've also read something about a Manual D(?) calculation relating to duct work.

What sort of questions should I ask as far as quality ductwork is concerned? What are "Tight Ducts"?

A TXV is better than a cap tube or fixed orfice because it can regulate the freon when the load changes. But really on a low efficient unit you probally would not notice a diff. With a higher efficient unit you would need txv to get the full efficiancy of the unit. As far as the aprilaire filter, I know the aprilaire 5000 was one of the better filters on the market using a media and a electronic together. But the last I heard there was a recall on the media were it could catch on fire, and no replacement media has been sent out yet. The only thing I could think of the tight ducts is the contracter sealing all the duct connections with a duct mastic. With out the duct mastic the duct would not be air tight you would get some leakage.

please post a reply on this one. When I install ducts I seal them no other options available. the law here requires it and I would think your laws do to. The only thing I can think of would be flex or hard pipe.

Duct leakage studies have shown that the typical unsealed residential duct installation leaks 30% or more of the total airflow through the unsealed seams. ACHR News has published the results of at least one of these studies in the past.

I believe SMACNA has also conducted such a study as well. The results of all the studies indicate that carefully sealing all sheet metal joints makes a great difference.

I had read that California (California already has its title 24 energy code) was considering adding duct sealing regulations to their installation code.

Is there more than one way to properly seal the ducts. I seem to remember one writer who advised using mastic and not just tape. So what is the best recommended way? Mastic alone, mastic plus tape?
Thanks

As far as sealing duct work, if its ductboard I staple all flaps then use foil tape. on "high end" jobs I use #6 mastic over the tape. Only time I've seen it come loose is if the area under the mastic is wet or damp. Also TXV systems are much better than piston or fixed meter types. You'll notice that TXV systems have a much higher SEER rating.

Originally posted by pipefitter2005 A TXV is better than a cap tube or fixed orfice because it can regulate the freon when the load changes. But really on a low efficient unit you probally would not notice a diff.

Any type of expansion valve will drastically improve both efficiency and effectiveness, NO MATTER what the pull it out of their rear seer rating the manufacturer is labeling the unit with.

The Tight ducts might just mean that the ducts have been tested and certified to be leak free. In Florida every house has to have a energy calculation and that calculation gives the house a score. The house has to have a score below 100 to pass. The program that does the calculation has an option for air tight ducts, but when you try to select that option it will tell you that the ducts have to be certified. This comes into play when a house is trying to get a better energy rating. I believe the the house has to get a score of 80 or below to qualify for a reduced interest rate. In addition the rating adds another selling point to the house.